Since the development of the first monoclonal antibodies by Koehler and Milstein in 1974, a lot of efforts have been dedicated to the development of antibodies which are appropriate for therapy in humans. The first monoclonal antibodies which became available had been developed in mice and rats. In the past ten years an ever growing number of human monoclonal antibodies or humanized monoclonal antibodies have reached the market. Well-known examples include for example Herceptin® and MabThera® from F. Hoffmann-La Roche AG, Basel.
A quite significant number of human or humanized monoclonal antibodies is under investigation and needs to be studied in experimental animals, before entry into human can be considered for the first trial purposes. Important criteria like bio-availability and antibody clearance just to mention two of them have to be studied.
Many of these studies require the quantification of the therapeutic antibody in the background of the experimental animal's own antibodies. In most cases mammals are used as experimental animals. Toxicology often is first assessed in rodents like mice or rats. In the more advanced stages of drug development, especially before entry of the drug into human beings, even monkeys have to be included into such pre-clinical studies.
Mammals usually have between about 10 to about 30 milligram of antibody per ml in the circulation. Therapeutic monoclonal antibodies typically have to be tested with serum levels ranging from about between 1 nanogram per ml to about 100 microgram per ml. The therapeutic antibody, thus, has to be detected against a background of experimental animal's antibodies which are in an excess of about 100-fold to 10 million-fold.
The detection of a human or humanized therapeutic antibody in the background of an experimental animal's antibody represents quite a significant task to the pharmacologist. The detection of a human or humanized antibody becomes more and more difficult the closer the test animal is related to H. sapiens. 
In WO 2008/031532 an anti-drug antibody assay is reported. The detection of a therapeutic antibody in an experimental animal is reported in WO 2006/066912. In U.S. Pat. No. 5,332,665 species specific, high affinity monoclonal antibodies are reported.